Simulations of the Last Glacial Maximum ice sheet surface climate: Implications for the interpretation of ice core air content

This paper reports on analyses of the surface pressure, surface wind, and s easonality of temperature and precipitation in the central parts of Greenla nd and Antarctica as simulated by different general circulation models (GCM s) for the present and for the Last Glacial Maximum (LGM) climates. These p arameters, in addition to the mean surface temperature, influence the air c ontent of the ice either directly or through their influence on the pore vo lume. To correctly interpret the air content of the ice in terms of past ic e sheet elevation changes, the variations of these parameters must therefor e be known. Most of the simulations discussed here have been carried out wi thin the framework of the Paleoclimate Modeling Intercomparison Project. Mo reover, a stretched grid GCM has been used with a high rc solution over the ice sheets. We show that not taking into account changes of surface pressu re at constant altitude between the LGM and today leads to an overestimatio n of past ice sheet elevation up to 150 m, while wind speed changes are too weak to have a significant influence on ice core air content. The results concerning changes of the amplitude or phase of the seasonal variations of precipitation and temperature are somewhat ambiguous. Most, but not; all, o f the models suggest an intensification of the seasonal cycle of surface te mperatures over central Greenland, and, to a lesser extent, over central Ea st; Antarctica. Neglecting these changes might lead to an underestimation o f past elevation by up to 140 m for the Greenland ice sheet, but this numbe r is subject to large uncertainties.